1. The problem statement, all variables and given/known data A loop-the-loop machine has radius 18m. What is the minimum speed at which a cart must travel so that it will safely loop the loop? 2. Relevant equations centripetal acceleration: v^2/r velocity=(2r*pi)/t Perhaps more? 3. The attempt at a solution To be honest, my main problem is that I'm not really sure where to start. I calculated the displacement a cart must travel, i.e. the circumference of the diameter, but I don't know what to do next..